Page MenuHomeFreeBSD

libusb: implement zlp flag in libusb transfer
Needs ReviewPublic

Authored by aokblast on Aug 6 2025, 12:58 PM.
Tags
None
Referenced Files
F132414151: D51759.id160030.diff
Thu, Oct 16, 5:52 PM
Unknown Object (File)
Sun, Oct 12, 3:09 PM
Unknown Object (File)
Sat, Oct 4, 3:40 AM
Unknown Object (File)
Thu, Oct 2, 11:32 PM
Unknown Object (File)
Thu, Oct 2, 11:05 PM
Unknown Object (File)
Thu, Oct 2, 2:25 AM
Unknown Object (File)
Wed, Oct 1, 8:26 AM
Unknown Object (File)
Tue, Sep 30, 9:15 AM
Subscribers
This revision needs review, but there are no reviewers specified.

Details

Reviewers
None
Summary

The USB protocol defines a Zero-Length Packet (ZLP) to signal the end of
a transfer when the data size is an exact multiple of the Maximum Packet
Size (MPS). Without a ZLP in such cases, the device may not be able to
determine that the transfer has completed.

This flag is added to libusb to allow the user send a ZLP in the end
of libusb_xfer.

Diff Detail

Repository
rG FreeBSD src repository
Lint
Lint Passed
Unit
No Test Coverage
Build Status
Buildable 66339
Build 63222: arc lint + arc unit

Event Timeline

Send packet only the multiple of packet

defer zlp check until we can find the xfer

lwhsu added inline comments.
lib/libusb/libusb10.c
1628

should we use libusb20_tr_get_max_packet_length() or libusb20_tr_get_max_total_length()?

This implemented is problematic since the correct way is to append a zero size TRB in TD instead of creating new TD. However, I think I am unable to make it work before 15.0 release. Therefore, I will modify it to at least we won't break any ABI for 15 if we want to merge later.